1. Field of the Invention
This invention relates to data backup software for computer systems. More particularly, the invention relates to a system and method for backing up a virtual disk image file used by a virtual machine.
2. Description of the Related Art
A virtual machine (VM), also referred to as a virtual computer, is a software implementation of a machine (computer) that executes programs like a real machine. Virtualization provides the ability for multiple virtual machines to run together on the same physical computer. Each virtual machine may execute its own operating system and may appear to a user of the virtual machine to be the same as an independent physical computer. The software layer that executes on the physical computer and manages the various virtual machines is called a hypervisor or virtual machine host software. The virtual machine host software can run on bare hardware (called a Type 1 or native VM) or under control of an operating system (called a Type 2 or hosted VM).
A user may interact with a virtual machine similarly as if the user were interacting with a physical computer. For example, various software applications may be installed on the virtual machine, and the virtual machine may enable the user to launch the software applications, provide input to the software applications, and view output from the software applications identically as if they were executing on a physical computer.
Just as a physical computer system uses files, a virtual machine also uses various files, such as operating system files, application software files, data files, etc. It is often necessary or desirable to backup the files used by a virtual machine. Backing up the files of the virtual machine helps to protect against data loss and corruption and also enables a previous state of the virtual machine to be recovered if necessary, e.g., to roll back the virtual machine to a state as it existed at a previous point in time.